Dr. Kent Brantly's condition is improving after being moved to the United States from Liberia, where he contracted the Ebola virus. Before leaving for Liberia, Brantly delivered a powerful sermon, saying that God had a call on his life.

"In October, [my wife] Amber and the kids and I are moving to Monrovia, Liberia, to work as medical missionaries at ELWA Hospital," Brantly told the Southeastern Church of Christ in Indianapolis. "For two years we will live and work and serve among the people who, until the last 10 years of peace, had known nothing but the violence and devastation of war for the previous 20 years."

Brantly added that he had "never been to Liberia" but was going "because God has a call on my life. God did not give us a spirit of timidity," he noted, quoting the Apostle Paul.

Unfortunately, Brantly contracted the Ebola virus while working in Liberia. He arrived in the United States on Saturday for treatment at a hospital in Atlanta, Georgia. Brantly was doing well enough that he was able to walk into the hospital rather than being carried in on a gurney. His family is happy to have him back in the States, where they can see him and speak with him, though they have to remain in a protective area.

"It was a relief to welcome Kent home today," his wife Amber said in a statement. "I spoke with him, and he is glad to be back in the U.S. I am thankful to God for his safe transport and for giving him the strength to walk into the hospital. Please continue praying for Kent and Nancy [Writebol, another American missionary infected with Ebola] and please continue praying for the people of Liberia and those who continue to serve them there."

Already, Brantly "seems [to have] improved from the reports we got earlier," Dr. Tom Frieden, director of the Centers for Disease Control and Prevention said on Sunday.

Nancy Writebol is expected to be flown to the United States for treatment on Tuesday. She will be flown in the same specially, CDC-outfitted plane that Brantly was flown in, and will receive treatment at the same Atlanta facility, which has one of the best Ebola units in the country. She and husband David will likely both return; David has not left her side since she was infected, and he has been in contact with their pastor in North Carolina.

"She is holding her own," Rev. John Munro said. She is in good spirits, he added.

Writebol reportedly received an experimental drug after Brantly sacrificed his dose so that she could be treated. The drug was intended to treat both Ebola patients, but there was only enough for one dose, so Brantly chose to give it to Writebol. However, the maker of the drug has said that Writebol never received the dosage.

"Our investigational therapy TKM-Ebola has not been given to either of the Samaritan Purse workers or anyone else infected in the current outbreak, and has not been given to anyone outside of our Phase I trials," Tekmira Pharmaceuticals said in a statement.

That means that Writebol's condition has not been affected by the experimental drug. Her husband has said that she is able to walk around a bit, which is a good sign.

"We can't wait to have her back home," Bruce Johnson, president of SIM USA, told NBC News.